Medium severity · published Mar 20, 2026
CVE-2026-4438
gethostbyaddr and gethostbyaddr_r return invalid DNS hostnames
5.4
CVSS
0.3%
EPSS
No
On KEV
Description
Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C library version 2.34 to version 2.43 could result in an invalid DNS hostname being returned to the caller in violation of the DNS specification.
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 26% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
GL
glibc · The GNU C Library
2.34 through 2.43 · source: vendor, NVD
SS
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.5 before V3.1.6; V3.1.5 before V3.1.6 · source: CISA
SS
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP · Siemens
V3.1.5 before V3.1.6; V3.1.5 before V3.1.6 · source: CISA
SS
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.5 before V3.1.6 · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4438
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-4438
Exploit
https://sourceware.org/bugzilla/show_bug.cgi?id=34015
cert-portal.siemens.com
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
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